Diesel engines are compression-ignition engines. That is, compression of air within the cylinder generates the heat required to ignite the fuel as it is injected. Compression ratios of 12:1 to 23:1 are common. Other factors affecting combustion in the diesel engine are combustion chamber design and fuel injection characteristics. Each of these factors is provided by the design of the various mechanical components of the engine. Fuel quantity is another factor affecting combustion in the diesel engine.
Fuel additives are employed to improve diesel engine performance. A wide variety of additives are known, including cetane number improvers which improve the ignition quality of the fuel, stabilizers, smoke reducing additives, corrosion inhibitors and detergents/dispersants.
In the diesel combustion process fuel vaporization and efficient mixing with available air are essential in insuring efficient combustion. The fuel injection equipment provides the mechanical means of achieving this and its performance is critical in controlling rate of fuel injection and fuel atomization. Optimum performance is only achieved when the fuel injection system is free from deposits and adjusted in accordance with the manufacturer's recommendations. There is, however, a tendency for diesel fuels to form deposits during distribution and combustion and these can markedly affect the combustion process.
Critical deposits can form in two basic areas. A buildup of gum or resinous degradation products can occur in the injection system. In severe cases this can result in sticking of pump plungers and injector pintles or needles. Problems often only occur on isolated cylinders, with the resultant misfire causing loss of power and increased exhaust smoke. Carbon deposits build up on the parts of the injector exposed to hot combustion gases, which can affect both fuel flow and fuel atomization characteristics of the injector. Again, loss in power, increased exhaust smoke and poor starting are the noticeable engine performance problems.
Deposit buildup in fuel pumps and injectors is not a new problem, but in recent years it is becoming more apparent, particularly in areas where fuels containing increased proportions of cracked components are being used.
Deposit buildup has been evident in both direct and indirect injection engines. Chemical additives have been used in attempts to control formation of deposits. Generally, the additives have been various nitrogen-containing compounds.
As mentioned hereinabove, deposits can operating and non-operating parts of injectors. It been found that of the many types of additives available in the art, those having the particular characteristics described in greater detail hereinafter provide exemplary cleanliness for both operating and non-operating parts of diesel fuel injectors.